Extend NS_SWIFT_UI_ACTOR to ListBindable and ListSectionController

[felixrosenvik]

New issue checklist

• I have reviewed the README and documentation
• I have searched existing issues and this is not a duplicate
• I have attempted to reproduce the issue and include an example project.

General information

• IGListKit version: 5.0.0
• iOS version(s): All
• CocoaPods/Carthage version:
• Xcode version: 15.3
• Devices/Simulators affected: All
• Reproducible in the demo project? (Yes/No): Yes
• Related issues:

Debug information

IGListKit recently added NS_SWIFT_UI_ACTOR to IGListAdapterDataSource and IGListSingleSectionControllerDelegate in this commit which is great, and helps remove many Swift Concurrency warnings. There are a couple more classes / protocols that could benefit from the same treatment.

---

• UICollectionViewCell is unable to conform to ListBindable due to "Main actor-isolated instance method 'bindViewModel' cannot be used to satisfy nonisolated protocol requirement". Doing a nonisolated implementation is not a viable option, as this would require the cell to do something like this:

nonisolated func bindViewModel(_ viewModel: Any) {
    Task { @MainActor in
        /* 
            Cell will be populated asynchronously, which could cause a flicker, 
            or break unit tests that expect the cell to be populated immediately.
        */
        titleLabel.text = viewModel.title
    }
}

• Subclassing ListSectionController is similarly problematic, as the functions it provides are currently non-isolated, but most of them will require calling UIKit, which is @MainActor isolated.

override func cellForItem(at index: Int) -> UICollectionViewCell {
    let cell: MyCell = collectionContext!.dequeueFromNib(for: self, index: index)
    /*
        "Main actor-isolated property 'titleLabel' can not be referenced from a non-isolated context"
    */
    cell.titleLabel.text = viewModel.title 
    return cell
}

These 2 instances are a couple examples that I spotted, but there could potentially exist more. I assume that IGListKit is underpinned by UICollectionViewDelegate/UICollectionViewDataSource which both are @MainActor/NS_SWIFT_UI_ACTOR, meaning that this addition could be quite straightforward.